1. Field of the Invention
The present invention relates to an exhaust device for discharging dust, heat, and the like generated inside a picture image forming apparatus, such as an electronic copying machine or a printer, and, more particularly, to such an exhaust device which is constructed in a manner so that the exhaust device is capable of exhausting dust, heat, etc., under conditions even when the exhaust device is positioned in proximity to an outside obstacle or the like.
2. Description of the Related Art
In picture image forming apparatus exemplified by electronic copying machines and printers, recorded paper bearing picture images are produced by an electrophotographic process in which an electrostatic latent image is formed by projecting a beam of picture image light onto a photosensitive material drum and feeding toner from a developing unit to form a picture image in toner on the drum in accordance with the latent image. Thereafter, the toner image is transferred onto printing paper by a picture image transfer device and the toner image bearing printing paper is passed through a fixing device which fixes the toner picture image on the paper and to produce image recorded paper. Apparatus of this type is prone to the development of interior dust and heat and is therefore provided with an exhaust device for discharging the dust and the heat to the exterior of the apparatus.
The dust generated inside the picture image forming apparatus is mainly paper dust from the paper transport system and clouds of toner from the circumference of the photosensitive material drum. In addition to such dust, large amounts of heat and steam, for example, are generated by the fixing device. Also, ozone and NOX (nitrogen oxide) are generated by a charging corotron and a transferring and separating corotron provided in positions facing the photosensitive material drum. The presence of such materials inside the apparatus cause deterioration of parts in the apparatus or otherwise interfere with maintenance-free operation of the apparatus. Moreover, unless the heat generated inside of the apparatus is discharged, the inside of the apparatus will reach high temperatures at which toner deteriorates. Additionally, the heat adversely influences other members, causing impediments to their operation.
Picture image forming apparatus conventionally employ an exhaust system for discharging the heat, dust, or ozone generated from within the apparatus. Dust and ozone filters are usually included to collect the dust and ozone, respectively. Such an exhaust system is disclosed, for example, in Japanese Patent Application Laid Open No. 37574-1985 (Showa 60). In the copying machine described, an exhaust system is arranged for each of upper and lower areas as divided from each other by a paper path in the main unit of the apparatus. These individual exhaust systems respectively discharge the heat generated from lamps and the like provided in the upper part of the apparatus and the heat generated from a power source, for example, in the lower part of the apparatus. These exhaust systems are constructed in such a manner to be capable of performing the exhausting function under favorable conditions, the timing for driving these exhaust systems being set up in accordance with the operating condition of the copying machine.
Conventional exhaust systems for apparatus of the type described employ a louvered register means for discharging the dust and heat through a side wall area of the main frame of a machine. However, the exhaust opening thus provided in a side wall area of a copying machine is often obstructed sufficiently to interfere with effective exhausting operation if the copying machine happens to be placed in a position close to another apparatus, for example, or close to a wall or the like. In order to prevent the occurrence of this problem, it is necessary to set the copying machine in a position spaced from other equipment. However, it is difficult in many cases to secure sufficient space for desks and other items in an office, particularly where a small sized copying machine may be used.
Moreover, it has been proposed, as illustrated in FIG. 9, that a louver 12 should be formed so as to project from a main unit frame 11 in a conventional copying machine like the example given above. The projecting louver 12 shown in FIG. 9 is provided with an exhaust port 13 formed on the upper surface of the projecting part, so that this construction, which clearly indicates the position of the exhaust device 10d to the operator, can prevent another object from being placed in a position close to the exhaust device. Yet, even with an exhaust device 10d so constructed, it will occasionally happen that the exhaust port of the projecting louver is obstructed if the copying machine is positioned close to a wall or the like. In some cases, such as compact printers, the exhaust port is arranged on the upper part of the apparatus. However, a problem with this construction is that the exhaust device is eventually obstructed with documents or the like placed on the upper area of the printer, which tends to happen in a small office space.